| Abstrakt: |
We have studied the expression of aldrin epoxidase (AE), 7-ethoxycoumarin-O-deethylase (ECDE), and aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH) in nine differentiated or dedifferentiated cell lines derived from H4IIEC3 rat hepatoma cells. The nature of the cytochromes P-450 mediating AE, ECDE and AHH activities was analysed using monoclonal antibodies (MAb) made to the major 3-methylcholanthrene-induced cytochrome P-450 (MAb-MC) or phenobarbital-induced cytochrome P-450 (MAb-PB) from rat liver. The cells were treated with 5 μM dexamethasone for 30 h to increase the levels of the monooxygenase activities. (a) The six differentiated cell lines examined (Faza967, Fao, HF1–4, 2sFou, C2Rev7, and H4IIEC3/G-) contained MAb-PB-sensitive AE comprising 30–75% of the total AE activity. In most of these cell lines MAb-PB also markedly inhibited ECDE; however, the antibody had a considerably weaker effect on AHH. (b) MAb-PB-sensitive AHH, ECDE and AE activities were also observed in untreated and phenobarbital-treated ceils. (c) MAb-MC inhibited AHH and ECDE in the two dedifferentiated lines HF1 and H5 by 50–80%. The antibody also inhibited AHH activities in the poorly differentiated line H41IEC3/T and in the majority of the differentiated lines by 40–65%. MAb-MC-sensitive AHH was found in Fao cells after treatment with benz[a]anthracene but not with dexamethasone. C2Rev7 cells did not contain detectable MAb-MC-sensitive AHH. (d) Benz[a]anthracene induced AHH in H4IIEC3/T, H4IIEC3/G-, and 2sFou cells 20–30-fold and in Faza967 and Fao cells 3–5-fold. Benz[a]anthracene remained without effect on AHH activity in C2Rev7 cells. various degrees phenobarbital-inducible The results show that the hepatoma cells examined express to cytochrome P-450 and/or 3-methylcholanthrene-inducible cytochrome P-450. These cell lines are versatile tools for studying the regulation of monooxygenase activities and analysing their role in the activation and inactivation of xenobiotics such as carcinogens, drugs and pesticides. [ABSTRACT FROM AUTHOR] |
